A hydrodynamic device for use with a recreational water vessel such as a surfboard, disrupts a flow of water under the recreational water vessel. The stationary mold comprises a stationary-side fixed plate on which are disposed four pillars to be inserted through a stripper and into a female insert assembly. The passageways extend through one or more ports penetrating the thickness of one of the plates thereby fluidly connecting the manifold to the opposite active surface of that plate, and the contacted electrode. The tank can receive at least one endoscope and includes injectors connected by a solenoid valve to the hermetic chamber. The services represent the quantity of energy generation as energy demands that the students may appreciate. The stimulating rays reflected from the reference plate are received with a light receiving device via a cut-off filter for transmitting light emitted by the sheet and blocking the red light, and an infrared ray image signal representing the infrared ray components of the stimulating rays is acquired.